java - java中的 "qualified this"构造是什么意思？

Question

在 Effective Java在“第 22 项:优先考虑静态成员类而不是非静态”项中，Josh Bloch 说:

Each instance of a nonstatic member class is implicitly associated with an enclosing instance of its containing class. Within instance methods of a nonstatic member class, you can invoke methods on the enclosing instance or obtain a reference to the enclosing instance using the qualified this construct.

他说的合格的这个构造是什么意思？

Answer 1

没有限定符，x() 将递归。使用限定符，将调用封闭实例的 x() 方法。

class Envelope {
  void x() {
    System.out.println("Hello");
  }
  class Enclosure {
    void x() {
      Envelope.this.x(); /* Qualified*/
    }
  }
}